I'm currently studying a CELTA and need some help with a lesson I'm teaching on Monday. I was wondering if some could help me with the following:

These questions are from "Cutting Edge: Upper Intermediate (p.36)".

In these dialogues, the students need to choose the best verb form and answer why. Choosing the best verb form is simple enough but can anybody help me as to why they're the best verb form to use?(Number 3 is causing me most problems) Any concept-checking questions or timelines to clarify will be much appreciated.

1. So how are you anyway? Done anything exciting since I last saw you?

No, nothing at all. It's rained / It's been raining all weekend. I haven't been / I haven't been going out once!

2. I'll phone you tonight to discuss the details, say about eight o'clock?

Could you make it a bit later? We'll have / We'll be having dinner at that time.

3. Excuse me, is it going to be much longer? I've waited / I've been waiting for over an hour!

I'm sorry, the computer's broken down / been breaking down and we've lost / we've been losing all our records. Dr Greenway will see you as soon as he can.

osman wrote:1. So how are you anyway? Done anything exciting since I last saw you?

No, nothing at all. It's rained / It's been raining all weekend. I haven't been / I haven't been going out once!

"...It's been raining..." - since it doesn't only tell on the result in the Present, but has to do with the process that influenced it; even more with the process than the result.Conversely:"...I haven't been out..." - points out the result, not the process.

Could you make it a bit later? We'll have / We'll be having dinner at that time.

"...We'll be having..." - it denotes a process at a given point on the scale of time; Continuous, as it were, stretches a point into a process.

osman wrote:3. Excuse me, is it going to be much longer? I've waited / I've been waiting for over an hour!

I'm sorry, the computer's broken down / been breaking down and we've lost / we've been losing all our records. Dr Greenway will see you as soon as he can.

"...I've been waiting..." - have waited and am still waiting."...has broken down..." - the focus of attention is on the result, not the process."have lost/have been loosing" - depends on what the speaker wants to say; since Dr Greenway isn't ready to see visitors, loosing data isn't over.